The U.S. is a nation of immigrants. The first wave of immigrants to colonial America, from England, France, Germany, and other northern European countries, were fleeing political and religious intolerance as well as seeking financial opportunities in the young country. Even then, the new arrivals faced open hostility and distrust from the populace. Regardless of the less than warm welcome, hopeful immigrants poured into the U.S. In fact, some 30 million immigrants entered the U.S. between 1870 and 1930.

As the U.S. sought to expand both geographically and economically in the early 19th century through the first decades of the 20th century, government officials and business leaders recognized that immigrants could fill the need for cheap labor and encouraged the flow of workers to the U.S. Between 1820 and 1930, the U.S. absorbed about 60% of the world’s immigrants. The U.S. didn’t begin to restrict its borders to immigrants until 1875, when it shunned “undesirables” and Chinese laborers. The 1875 policy was the first of many attempts to limit the number of immigrants entering the U.S. Most policies and attempts at enforcement have failed. Indeed, according to 2010 census figures, more than 11 million people live in the U.S. illegally.

This primer on immigration details milestones in immigration and the many laws passed related to immigration, lists dozens of facts and statistics about immigrants and immigration, outlines the process involved in obtaining a Green Card, and more.